Task Coach 1.2.21 was released on June 25, 2011, whereas the portage contains only 1.2.16. Please update the portage. I noticed no changes in the build process. Renaming the ebuild was sufficient for me to get the new version working. Seems OK on ~amd64.
Bumped to 1.2.23
Forgot to close this. Anyway 1.2.24 it is.